The present invention relates generally to a new and improved machine for opening a taphole in a shaft furnace and for plugging the taphole. More particularly, this invention relates to a combined machine, that can open a taphole in a shaft furnace, plug up the taphole by injecting a plugging mass and then drive a piercing rod into the plugged taphole prior to the plugging mass being fully hardened.
Various machines have been provided for opening a taphole in a wall of a shaft furnace in accordance with a process known as the lost rod method. In this process,the taphole is plugged or closed with a plugging mass, a metal rod is driven into the plugging mass before it has completely hardened and, at the desired moment, the metal rod (or piercing rod) is removed to open the taphole. Such machines comprise a mount for supporting a piercing rod, a suspension structure for the mount designed to displace the mount from a parked position away from the taphole into an operating position in which the mount is located in the extension of the axis of the taphole. Drive means are installed on the mount to develop a pulling force or pushing force, respectively as required, parallel to the longitudinal axis of the mount. In this case, a coupling device which can be displaced on the mount is connected to the drive means in order to transmit the pushing force to a piercing rod supported on the mount in order to drive it into the plugging mass previously injected into the taphole, or to transmit the pulling force to a piercing rod sealed in the hardened plugging mass to remove this rod from the taphole. Various operating principles for such machines are, for example, described in Patent Specifications EP-0,379,018 (corresponding to U.S. Pat. No. 5,192,489), LU-87,915, LU-88,029 (corresponding to U.S. application Ser. No. 968,984 filed Oct. 30, 1992), LU-88,058 (corresponding to U.S. application Ser. No. 008,128 filed Jan. 22, 1993), LU-88,059 (corresponding to PCT application WO 93/15 231), LU-88,060 (corresponding to U.S. application Ser. No. 008,129 filed Jan. 22, 1993) and LU-88,135 (corresponding to U.S. application Ser. No. 080,145 filed Jun. 17, 1993), all of the contents of the foregoing patents and applications being incorporated herein by reference. It should be pointed out that, on all these machines, there also exists the possibility of drilling the taphole using a conventional drill bit driven by a rotary work device which can also be displaced on the mount by the aforementioned drive means.
Besides a boring machine, it is essential to have available a plugging machine in order to be able to inject the plugging mass into the taphole. Such a plugging machine comprises, in a known manner, its own suspension structure for displacing a plugging device from a parked position away from the taphole into a plugging position in which it is aligned with the axis of the taphole and means to force the plugging device firmly against the wall of the furnace during the plugging operation. The plugging device of a plugging machine comprises a plugging chamber to receive the plugging mass, a plugging snout, a piston to expel the plugging mass, fitted in the plugging chamber, and a powerful hydraulic jack arranged in the axis of the expulsion piston to displace the expulsion piston axially in the plugging chamber and thus inject the plugging mass under pressure through the plugging snout into the taphole.
The presence of two machines, namely a boring machine and a plugging machine constitutes two major problems. The overall size of the two machines fills up the work area around the shaft furnace and makes it difficult to operate efficiently and with safety. In addition, the cost of two separate machines is high and, particularly, the investment costs are especially severe for small shaft furnaces.
A combined machine which can be used both for opening the taphole in a shaft furnace and for plugging the taphole with a plugging mass is therefore needed. This would be both economical, space saving and increase the safety of the work place.